Four large hydropower stations have recently been built downstream the; Jinsha River in Southwestern China with a strong regional tectonic; activity background. There is widely felt seismicity since the; impoundment of the Xiluodu and Xiangjiaba reservoirs, increasing the; public concern in this region. We begin with a criticality analysis of; the faults near these reservoirs to quantify their susceptibility to; triggered seismicity. Then we focus on the Xiluodu reservoir to; investigate the correlation between the impoundment and seismicity; nearby. We analyze the spatio-temporal distribution of seismicity near; the Xiluodu reservoir, and identify the plausible rapid and delayed; seismic response due to the impoundment. According to the impoundment; record, we explicitly model the hydro-mechanical changes due to; diffusion and reservoir water load, i.e., in pore pressure, elastic; stress, and the resulting Coulomb stress. Our results show that the pore; pressure changes can reach a level that may trigger fault reactivation; and consequently, seismicity nearby. The water load can also induce the; positive Coulomb stress changes on faults, depending on the fault; orientation, which is especially important for understanding the; earthquakes that occurred shortly after the impoundment and at more than; 10 km distance from the reservoir. The combination of these two effects; can induce positive Coulomb stress change over a larger area, which; overlaps the majority of the events after the impoundment. While the; causal relationship between the impoundment and seismicity warrants; further analysis, we hope to inform the regional seismic impact of; impoundment with this timely study.
